An image sensor is a device including several million photoelectric conversion devices for converting light into an electric signal, based on the intensity of light received by the device. The image sensor can be used in a digital input device which digitalizes recorded images. This technology is rapidly developing, and there is increasing demand for devices in various applications such as security devices and digital porters.
Image sensors include a pixel array in which a plurality of pixels is arranged in a matrix form. Each pixel includes a photo-sensing device and a transmitting and signal output device. Image sensors are broadly categorized as charge-coupled device (CCD) image sensors and complementary metal oxide semiconductor (CMOS) image sensors, depending upon the transmitting and signal output device therein. CMOS image sensors concentrate external light through microlenses, and the concentrated light is transmitted to a photo-sensing device such as a photodiode that outputs a signal.
CMOS image sensors can be further modified to increase resolution. Recent research has focused on decreasing pixel size down to 1 μm or less. Because a small pixel size of 1 μm or less receives 1.5 times the visible ray wave length, its geometric and wave optical aspects in relation to the microlenses have to be considered. Further, as the unit pixel becomes smaller, the diameter of each microlens becomes smaller. Accordingly, unless the lenses have a shorter focal distance, a crosstalk phenomenon between adjacent pixels more easily occurs, which can deteriorate resolution.
In order to solve this problem, the thickness of each layer disposed between the photodiode and the microlens can be reduced. Conventional layers have included a thermally-curable resin composition, such as a resin composition including a self-curable copolymer and an epoxy compound.